1. Field of the Invention
The present invention relates generally to magnetic heads for hard disk drives, and more particularly to a heating device for the localized heating of the pole tip of the magnetic head.
2. Description of the Prior Art
The continual quest to increase the areal data storage density of magnetic media has resulted in the reduction in the width of the writing head magnetic pole tip of the magnetic head, such that a narrower track width is created and more tracks per inch (TPI) can be recorded in the media. Simultaneously, there is the quest to increase the data rate at which data bits are written to the magnetic media. State of the art pole tips are currently created having a pole tip width of approximately 0.25 microns in response to the desire to increase TPI, and data rates are approaching 1 Gb/second. A problem that arises when such narrow pole tips are driven at such high data rates is that rapid magnetic domain switching within the narrow pole tip at such data rates has become difficult to obtain. Experimental evidence shows that the magnetization of such a narrow pole tip is switching at a much slower rate than that of the much wider yoke behind the pole tip, and it appears that for such very narrow pole tips at these high data rate frequencies that the pole tip is no longer acting as a soft magnet, but almost as a tiny hard magnet, with its magnetization being switched back and forth (rather than rotating) to accomplish the high data rate writing.
The sluggishness of the pole tip switching appears to be due, in part, to its small dimensions, which are approaching the dimensions of magnetic domains within the pole tip, as well as the high local stress levels within the pole tip. The small sub-domain dimensions reduce the local permeability of the pole tip through stress-induced anisotropy, and through the relatively slow domain wall motion involved in the switching action. There is therefore a need to increase the permeability and reduce the stress of the narrow pole tip, such that magnetic flux will flow more rapidly through it and the magnetization switching rate of the pole tip can be increased.